Fluid coupling

ABSTRACT

Two coupling members are provided in respective butting end faces thereof with annular recessed portions surrounding respective fluid channels thereof and having annular projections each formed in a bottom face of the recessed portion. A gasket comprises a sealing portion having an outside diameter smaller than the diameter of the recessed portions and is positioned between the projections of the coupling members, and a guide has an outside diameter permitting the guide to be fitted into the recessed portions and positioned externally of the sealing portion. The butting end faces of the coupling members are movable into contact with each other when the coupling is tightened up properly. The sealing portion has an annular groove formed in an outer periphery thereof, and the sealing portion and the guide are connected together by a snap ring fitted in the annular groove.

TECHNICAL FIELD

The present invention relates to fluid couplings, and more particularlyto fluid couplings comprising a gasket which gives predetermined sealingproperties to the coupling when deformed.

PRIOR ART

FIG. 4 shows a fluid coupling already known. With reference to thisdrawing, first and second coupling members 41, 42 provided with annularprojections 41 a, 42 a on opposed faces thereof are butted against eachother with a gasket 43 interposed therebetween. A cap nut 44 screwed onthe first coupling member 41 is tightened up to deform the gasket 43 andgive a proper sealing force. Indicated at 45 is a thrust ring forfacilitating the rotation of the cap nut 44.

With such a fluid coupling, the proper amount of rotation to be given tothe cap nut 44 after the nut is manually tightened is predetermined soas to obtain the proper sealing force by pretightening the nut manuallyand fully tightening up the nut with a jig. To ensure the proper sealingforce, it is also practice to measure the torque of tightening the nutand to cease tightening when a proper torque is given.

When the conventional fluid coupling is handled actually, it is likelythat the coupling will be tightened up to excess or the sealing forcewill differ from worker to worker. Although the worker intends to ensurethe proper amount of rotation or the proper torque, there arises theproblem of faulty tightening due to a difference from the proper value.

An object of the present invention is to provide a fluid coupling whichis made free of faulty tightening such as excessive tightening.

DISCLOSURE OF THE INVENTION

The present invention provides a fluid coupling comprising a first and asecond coupling member having respective fluid channels in communicationwith each other, an annular gasket interposed between butting end facesof the two coupling members, and screw means for connecting the twocoupling members together, each of the coupling members being providedin the butting end face thereof with an annular recessed portionsurrounding the fluid channel thereof and having an annular projectionformed in a bottom face of the recessed portion, the gasket comprising asealing portion having an outside diameter smaller than the diameter ofthe recessed portion and positioned between the annular projections ofthe two coupling members, and a guide having an outside diameterpermitting the guide to be fitted into the recessed portion andpositioned externally of the sealing portion, the butting end faces ofthe two coupling members being movable into contact with each other whenthe coupling is tightened up properly.

With the fluid coupling of the present invention, the sealing portion ofthe gasket is deformed by tightening the coupling to produce a sealingforce, and further continued tightening of the coupling moves thebutting end faces of the two coupling members into contact with eachother. This makes it impossible to tighten up the coupling any longer,consequently precluding the coupling from being tightened excessively orinsufficiently. The guide restrains the coupling member from shiftingradially thereof beyond a predetermined range.

The sealing portion of the gasket and the guide thereof may be in theform of an integral piece but are preferably connected togetherseparably, for example, by a snap ring. Stated more specifically, thesealing portion preferably has an annular groove formed in an outerperiphery thereof to connect the sealing portion and the guide togetherby a snap ring fitted in the annular groove. To connect the sealingportion and the guide together effectively and to make it possible toposition the guide relative to the sealing portion radially thereof inthis case, it is desirable to form an annular groove also in an innerperiphery of the guide.

It is further desirable that the guide comprise a large-diameter portionfitting in the recessed portion of one of the coupling members withoutplay and a small-diameter portion loosely fitted in the recessed portionof the other coupling member. This structure prevents the guide frommoving relative to the above-mentioned one coupling member radiallythereof to restrain the other coupling member from moving relative tothe guide radially thereof beyond the predetermined range, consequentlypreventing a fault from developing in the sealing properties owing to ashift.

Preferably, the guide is separably connected to one of the couplingmembers by a snap ring so as not to slip out of the coupling member.Stated more specifically, the guide preferably has an annular furrowformed in an outer periphery of the large-diameter portion thereof toconnect the guide and one of the coupling members together by a snapring fitted in the annular furrow. This prevents the gasket frominadvertently slipping out of the coupling member when the coupling isdisassembled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a gasket for use in a fluid coupling accordingto the invention.

FIG. 2 is a view in longitudinal section showing the fluid coupling ofthe invention as tightened manually.

FIG. 3 is a view in longitudinal section showing the fluid coupling ofthe invention as completely tightened up.

FIG. 4 is a view in longitudinal section showing a conventional fluidcoupling.

BEST MODE OF CARRYING OUT THE INVENTION

An embodiment of the invention will be described below with reference tothe drawings.

The fluid coupling of the invention has a structure for joining twocoupling members 1, 2 fluid-tightly. The coupling comprises first andsecond coupling members 1, 2 having respective fluid channels 1 a, 2 acommunicating with each other, an annular gasket 10 interposed betweenbutting end faces of the two coupling members 1, 2, and screw means forfastening the coupling members 1, 2 together. (Although the screw meansis not shown, various known means are usable such as the one shown inFIG. 4.)

Annular recessed portions 3, 4 surrounding the openings of the fluidchannels 1 a, 2 a are formed in the butting end faces of the first andsecond coupling members 1, 2, respectively, and annular projections 5, 6are formed in the bottom faces of the recessed portions 3, 4.

The gasket 10 comprises an annular sealing portion 11 positioned betweenthe annular projections 5, 6 of the coupling members 3, 4, and anannular guide 12 attached to the outer periphery of the sealing portion11 by a snap ring 13.

The sealing portion 11 is made of stainless steel and is a portionserving the same function as conventional gaskets and having an outsidediameter smaller than the diameter of the annular recessed portions 3, 4of the coupling members 1, 2 and an inside diameter approximately equalto the diameter of the fluid channels 1 a, 2 a of the coupling members1, 2. The annular projections 5, 6 of the coupling members 1, 2 are soprovided as to come into contact with the midportion of the sealingportion 11.

The sealing portion 11 is provided in its outer periphery with anannular groove 14 for the snap ring 13 to fit in. The snap ring 13 isC-shaped so as to exhibit elasticity, has an outside diameter greaterthan the inside diameter of the guide 12 when in a free state andprevents the guide 12 from slipping off from the sealing portion 11 byvirtue of the elastic force of the ring 13 acting to expand radiallyoutward. The diameter of the bottom face of the sealing portion 11 whichface defines the annular groove 14 is smaller than the inside diameterof the snap ring 13 in its free state, and the snap ring 13 is notrestrained from moving radially inwardly thereof. Accordingly, the guide12 and the sealing portion 11 are held connected together unlesssubjected to a force from outside and can be readily separated from eachother when subjected to a force greater than the elastic force of thesnap ring 13.

The guide 12 is made of stainless steel and has such an outside diameterthat the guide 12 can be fitted into the annular recessed portions 3, 4of the coupling members 1, 2, and such an inside diameter as to fitaround the sealing portion 11. Stated more specifically, the guide 12comprises a large-diameter portion 12 a fittable into the annularrecessed portion 3 of the first coupling member 1 without play and asmall-diameter portion 12 b loosely fittable into the annular recessedportion 4 of the second coupling member 2. The large-diameter portion 12a is provided in its outer periphery with an annular furrow 16 for asnap ring 15 to fit in. The snap ring 15 is C-shaped so as to beelastic, has an outside diameter larger than the diameter of the annularrecessed portion 3 of the first coupling member 1, accordingly, largerthan the outside diameter of the large-diameter portion 12 a of theguide 12 when in a free state, and is projected outward beyond the outerperiphery of the large-diameter portion 12 a as shown in FIG. 1. Theelastic force of the snap ring 15 acting to expand radially outwardlythereof holds the guide 12 on the first coupling member 1. The diameterof the bottom face of the large-diameter portion 12 a which face definesthe annular furrow 16 is smaller than the inside diameter of the snapring 15 in its free state, and the snap ring 15 is not restrained frommoving radially inwardly thereof. When the coupling members 1, 2 areseparated from each other, therefore, the gasket 10 is prevented fromslipping out of the coupling member 1 while the gasket is not subjectedto a force from outside. If subjected to a force greater than theelastic force of the snap ring 15, the gasket 10 is removable from thefirst coupling member 1 with a small force.

The guide 12 is provided in its inner periphery with a V-shaped shallowgroove 17 for fitting therein an outer peripheral portion of the snapring 13 to hold the sealing portion 11 and the guide 12 together. Thismakes it more difficult for the guide 12 to slip off from the sealingportion 11, also serving to position the guide 12 in place relative tothe sealing portion 11 radially of the sealing portion 11.

FIG. 2 shows the fluid coupling of the invention as tightened manually.With reference to this drawing, the value obtained by adding thecombined height of the annular projections 3, 4 of the two couplingmember 1, 2 to the entire thickness of the sealing portion 11 of thegasket 10 is slightly greater than the combined depth of the recessedportions 3, 4 of the two coupling members 1, 2. A gap G is thereforeformed between the butting end faces (the portions having no recesses 3,4) of the two coupling members 1, 2.

FIG. 3 shows the fluid coupling of the invention as tightened upproperly. With reference to this drawing, the gap G existing in themanually tightened state of FIG. 2 is reduced to zero. With the fluidcoupling of the present invention, the gap G between the butting endfaces of the two coupling members 1, 2 as tightened manually is madeequal to the proper amount of tightening, and when the coupling istightened up properly, the butting end faces of the two coupling members1, 2 come into contact with each other. Accordingly, when the couplingis tightened with a jig, the sealing portion 11 of the gasket 10 isdeformed first to produce a sealing force, and when the coupling istightened up continuously, the butting end faces of the two couplingmembers 1, 2 come into contact with each other, permitting the couplingto be tightened no longer and thus precluding excessive tightening orinsufficient tightening.

Incidentally, not the large-diameter portion 12 a of the guide 12 butthe small-diameter portion 12 b thereof is shown in FIG. 2 as fitted inthe second coupling member 2, which is therefore likely to shiftcorrespondingly. However, since the annular projections 5, 6 of the twocoupling members 3, 4 are adapted to come into contact with themidportion of the sealing portion 11, such a shift will not displace theannular projections 5, 6 from the sealing portion 11, hence noimpairment of sealing properties.

INDUSTRIAL APPLICABILITY

The invention provides a fluid coupling which is suitable for use influid control devices, for example, of semiconductor fabricationapparatus as a coupling for connecting fluid control units togetherfluid-tightly.

The invention claimed is:
 1. A fluid coupling comprising a first and asecond coupling member having respective fluid channels in communicationwith each other, an annular gasket interposed between butting end facesof the two coupling members, and screw means for connecting the twocoupling members together, each of the coupling members being providedin the butting end face thereof with an annular recessed portionsurrounding the fluid channel thereof and having an annular projectionformed in a bottom face of the recessed portion, the gasket comprising asealing portion having an outside diameter smaller than a diameter ofthe recessed portion and positioned between the annular projections ofthe two coupling members, and a guide having an outside diameterpermitting the guide to be fitted into the recessed portion andpositioned externally of the sealing portion, the butting end faces ofthe two coupling members being movable into contact with each other whenthe coupling is tightened up properly, wherein the sealing portion hasan annular groove formed in an outer periphery thereof, and the sealingportion and the guide are connected together by a snap ring fitted inthe annular groove.
 2. A fluid coupling comprising a first and a secondcoupling member having respective fluid channels in communication witheach other, an annular gasket interposed between butting end faces ofthe two coupling members, and screw means for connecting the twocoupling members together, each of the coupling members being providedin the butting end face thereof with an annular recessed portionsurrounding the fluid channel thereof and having an annular projectionformed in a bottom face of the recessed portion, the gasket comprising asealing portion having an outside diameter smaller than a diameter ofthe recessed portion and positioned between the annular projections ofthe two coupling members, and a guide having an outside diameterpermitting the guide to be fitted into the recessed portion andpositioned externally of the sealing portion, the butting end faces ofthe two coupling members being movable into contact with each other whenthe coupling is tightened up properly, wherein the guide comprises alarge-diameter portion fitting in the recessed portion of one of thecoupling members without play and a small-diameter portion looselyfitted in the recessed portion of the other coupling member, and whereinthe guide has an annular furrow formed in an outer periphery of thelarge-diameter portion thereof, and the guide and one of the couplingmembers are connected together by a snap ring fitted in the annularfurrow.